Device for physical exercise

ABSTRACT

To improve the dynamic response, a method is described for managing a physical exercise device (10) comprising an endless belt (16) to create a track on which a user (U) can walk or run, and an electric motor (30) to slide the belt.The method has the steps of controlling the driving torque applied by the electric motor (30) to the belt (16) so that the driving torque is proportional to the force component (F), or to the torque, which the user imparts on the belt (16) to advance on the belt (16).

The present invention relates to a device for physical exercise havingan endless walkable surface, and more particularly to a treadmill havinga motorized endless belt.

The most simple treadmills are usually motorized, with the speed of thebelt being adjustable by the user.

Other more sophisticated motorized treadmills, which do not require theuser to manually adjust the speed of the belt, can be classified intotwo types. The first type adjusts the belt speed as a function of theuser's biological functions while the second type adjusts the belt speedas a function of the user's position relative to the treadmill.

The most common variety of the first type automatically controls thebelt speed as a function of the user's heart rate, see e.g. U.S. Pat.No. 3,518,985.

The treadmills of the second type allow the user to adjust the speed ofthe belt simply by changing his pace, thereby more closely simulatingnatural conditions. See e.g. FR 1,565,617, U.S. Pat. Nos. 1,919,627 and4,708,337.

In FR 1565617 there are sensors at the sides of the treadmill to detectthe user's location. Each sensor consists of a photocell. U.S. Pat. No.1,919,627 implements an automatic control based on the user's bodyposition with respect to an electrostatic sensor attached to thetreadmill. In U.S. Pat. No. 4,708,337 the belt is driven by a motorautomatically controlled by the user's body position detected by anultrasonic sensor mounted on the control panel.

However, all these models have the great disadvantage of onlyapproximately simulating the stress of a real walk or run. It is a factthat the same distance travelled without a treadmill involves a muchgreater energy expense, because the treadmill facilitates too much thestride and the athlete must not shift his weight forward but only liftit temporarily.

The main object of the invention is to improve this state of the art.

Other main object of the invention is to provide a device for physicalexercise having an endless walkable surface, more particularly atreadmill having a motorized endless belt, which simulates more closelythe conditions of running or walking on the ground.

These and other objects are achieved by a device according to claim 4;other advantageous technical features are defined in the dependentclaims.

A first aspect of the invention is a method for managing a physicalexercise device comprising

an endless belt to create a track on which a user can walk or run,

an electric motor to slide the belt,

with the steps of

controlling the driving torque applied by the electric motor to the beltso that the driving torque is proportional to the force component, or tothe torque, which the user imparts on the belt to advance on the belt.

Another aspect of the invention is a device for physical exercisecomprising:

-   -   an endless belt to create a track on which a user can walk or        run,    -   an electric motor to slide the belt,    -   a sensor for generating an electrical signal indicative of the        force component, or indicative of the torque, that the user        imparts on the belt for advancing on the belt,    -   an electronic circuit configured for        -   reading the sensor's signal, and            -   controlling the driving torque applied by the electric                motor to the belt so that the driving torque is                proportional to said component or said torque imparted                by the user.

The motor is preferably controlled only as a function of the forcecomponent or torque alone, discharged by the user on the belt, which isresponsible for the forward motion for walking or running (the weightforce is e.g. neglected because orthogonal to the motion).

To evaluate the torque or force applied by the user e.g. the vectorcomponent of the force that the user imparts on the belt is measured,component of which—in particular—the weight is only a part. The dynamicforce generated by the muscles of the legs is added to the weight andthus the total thrust vector is determined.

The user's weight force is preferably measured to evaluate only, oralso, the physical stress and/or the actual calories consumed.

To evaluate the torque imparted by the user on the belt, preferably thetorque imparted on a roller or on an axle that supports the belt ismeasured, by means of e.g. a rotating torsiometer or a generic torquesensor.

A variant provides to control the motor by measuring only the weight ofthe person, that is, the force exerted on the belt and directeddownwards. Since between weight and force of tangential thrust there isenough proportionality, the force or torque imparted on the belt can becalculated or indirectly estimated from the weight.

The motor's torque, being proportional to said force or torque impressedby the user, returns to the belt (and to the foot) a force proportionalto that imparted by the user.

The control of driving torque applied by the electric motor to the beltis open to many variations, all included in the general inventiveconcept of the method or device.

According to a first preferred variant, the driving torque is regulatedfor transmitting to the belt a force or torque in the same direction tosaid force or torque generated by the user. In this way, the motorassists the stride, which is facilitated (useful condition e.g. forelderly or disabled people during recovery therapies of the lowerlimbs).

According to a second preferred variant, the driving torque is adjustedto transmit to the belt a force or torque having a direction opposite tothat of said force or torque generated by the user. In this way themotor opposes the stride, and simulates e.g. an uphill or the actualresponse of a ground. Preferably in these variants the electroniccircuit is configured to, or the microprocessor is programmed to,execute the motor control according to the above logic.

To simplify the detection, there is detected a force imparted by theuser along a direction parallel to the sliding direction of the beltand/or a direction parallel to that of the supporting surface on whichthe device is placed.

E.g. said force is detected at a point located between the device andthe floor, and/or

on and/or under the surface of the belt, and/or

on the user's shoes.

Preferably, the electric motor is an axial-flux motor.

The sensor can be realized in many ways. E.g. with

one or more load cells placed between the device and the floor, and/or

one or more load cells placed on and/or under the belt, and/or

one or more load cells placed in the user's shoes and communicating withthe electronic circuit e.g. by wireless radio means.

Each load cell may be replaced e.g. even by a strain gauge or a pressuresensor.

The electronic circuit is preferably a microprocessor, but it is alsopossible to implement it with a discrete-component circuit board. Themicroprocessor is programmable and allows great freedom to implementintelligent functions.

Preferably the device comprises a low-pass filter for filtering thesignal generated by the sensor before sending it to the electroniccircuit. The sensor is likely to emit a pulse signal with peaks at theinstants when the foot leans, while the signal will be smaller or zerowhen the user is “in flight” over the belt. The filter is configurede.g. to level the signal and/or to extract the average thereof orhowever to restrict the signal to less fluctuating values. E.g. a peakdetector can also be used.

The filter may be implemented in the digital domain by programming themicroprocessor.

Preferably the device comprises a user interface, such as e.g. atouch-screen or a keyboard, configured to detect a user selectiondirected to adjust the value of a constant of proportionality betweenthe torque transmitted to the belt and the force generated by the user.The electronic circuit may detect the user's selection and in accordancewith the proportionality constant regulates the driving torque of themotor transmitted to the belt. As mentioned, the proportionalityconstant can be positive or negative.

Another aspect of the invention is a program that, when loaded into aprocessor, performs one or each activity or method step as definedabove.

Further advantages will become apparent from the following description,which refers to a preferred embodiment in which:

FIG. 1 shows a diagram of a treadmill.

A treadmill 10 is illustrated schematically in FIG. 1, and comprises abase frame 14 on which are mounted two rollers 12 which support awell-known endless belt 16 on which a user U can place his feet P in theact of walking or running on the spot.

The base frame 14 rests on a floor T through feet 18, on or in or underwhich are mounted one or more load cells 22.

At least one of the two rollers 12 is coupled with an electric motor 30for receiving rotary motion and move the belt 16.

The electric motor 30 is controlled by a microprocessor 40 through knownpower electronics stages (not shown), e.g. an inverter. The arrows inFIG. 1 indicate signal lines.

The microprocessor 40 is also connected to the load cells 22, to readthe emitted signals therefrom, and to an (optional) data input userinterface 50, e.g. a touchscreen. Through the user interface 50 the usercan program a proportionality constant, useful for adjusting theoperation of the treadmill 10.

The cells 22 are installed so as to emit a signal indicative of theforce that a foot P of a user U exerts onto the belt 16 during theexercise. From the measured force the weight of the user U isdisregarded, while only the component F parallel to the surface of thebelt 16 and/or to the surface of the floor T is considered. One may alsomeasure a different force or at different points, and extract orcalculate therefrom the component F parallel to the belt surface 16and/or to the floor T's surface.

The cells 22 may be replaced by any sensor capable of generating anelectrical signal proportional to or indicative of the component of thethrust generated by the foot P which, on the floor T and without thetreadmill 10, would move the user U's body forward. To this force, asexplained below, the device reacts by generating a proportional force ortorque on the belt 16.

In the microprocessor 40 the signal generated by the cells 22 iscompared in a circuit 42 with a signal which expresses theproportionality constant entered with the user interface 50. Thecomparison is e.g. a subtraction to generate an error term.

The result of the circuit 42 is processed by a gain stage 44 which emitscontrol signals for the electric motor 30 so that the latter develops acertain torque and imposes a force to the endless belt 16 in dependenceof the signal emitted by the circuit 42.

Preferably, for greater accuracy, the electric motor 30 is also feedbackcontrolled thanks to a signal line 32 which returns to the stage 44 afeedback signal from the electric motor 30.

As it can be seen, the microprocessor 40 implements a feedback controlin which the proportionality constant entered with the user interface 50becomes a reference signal for adjusting the torque imparted by theelectric motor 30 to the endless belt 16. Then, according to the valueof this proportionality constant, the electric motor 30 can impart tothe endless belt 16 a force opposite to that imparted by a foot P(resistance to the stride), or a force in the same direction (assistanceto the stride).

In another exemplary embodiment, the circuit 42 is a multiplicationblock, in which the signal coming from the cells 22 is multiplied by theconstant of proportionality. The result of the multiplication is inputto the stage 44 as a torque reference for the motor 30. The stage 44then acts on the motor 30 for making it develop a torque which tracksthe reference.

Since the cells 22 generate a pulse signal, with peaks having cadence ofthe stride, it is preferable to filter it with a low pass filter 52,e.g. a digital filter implemented numerically in the microprocessor 40.Thus, the torque reference for the motor 30 has a less oscillatorytrend.

1. Method for managing a physical exercise device (10) comprising anendless belt (16) to create a track on which a user (U) can walk or run,and an electric motor (30) to slide the belt, with the steps ofcontrolling the driving torque applied by the electric motor (30) to thebelt (16) so that the driving torque is proportional to the forcecomponent (F), or to the torque, which the user imparts on the belt (16)to advance on the belt (16).
 2. Method according to claim 1, wherein thedriving torque is regulated to transmit to the belt a force or torquethat has equal direction as said force or torque generated by the user.3. Method according to claim 1, wherein the driving torque is regulatedto transmit to the belt a force or torque having opposite direction tothat of said force or torque generated by the user.
 4. Physical exercisedevice (10) comprising: an endless belt (16) to create a track on whicha user (U) can walk or run, an electric motor (30) to slide the belt, asensor (22) for generating an electrical signal indicative of the forcecomponent, or indicative of the torque, that the user imparts on thebelt for advancing on the belt, an electronic circuit (40) configuredfor reading the sensor's signal, and controlling the driving torqueapplied by the electric motor (30) to the belt (16) so that the drivingtorque is proportional to said component or said torque imparted by theuser.
 5. Device according to claim 4, wherein the electronic circuit(40) is configured to regulate the driving torque so as to transmit tothe belt (16) a force or torque that has same direction as said force ortorque generated by the user.
 6. Device according to claim 4, whereinthe electronic circuit (40) is configured to regulate the driving torqueso as to transmit to the belt (16) a force or torque having oppositedirection to that of said force or torque generated by the user. 7.Device according to claim 4, wherein the sensor (22) is configured todetect a force imparted by the user along a direction (F) parallel tothe sliding direction of the belt and/or a direction parallel to that ofthe supporting surface (T) on which the device is placed.
 8. Deviceaccording to claim 4, wherein the sensor (22) is placed at a pointlocated between the device and the supporting surface (T), and/or onand/or below the surface of the belt, and/or on the user's shoes. 9.Device according to claim 4, wherein the sensor (22) is a load cell, ora strain gauge or a pressure sensor.
 10. Device according to claim 4,comprising a low-pass filter for filtering the signal generated by thesensor before sending it to the electronic circuit.